A sheet processing apparatus receives recording media having images formed thereon discharged from an image forming apparatus and executes post-processing such as stapling, punching, or saddle folding. In particular, concerning the saddle folding, a reduction in time for the processing is demanded.
For example, JP-A-2003-2532 discloses a technique for executing saddle folding at low speed, i.e., high torque until saddle-folded recording media are conveyed by a predetermined distance from a nipping position of a pair of saddle folding rollers that saddle-fold the recording media and thereafter discharging the recording media at high speed.
However, when a large number of recording media are saddle-folded, it is necessary to saddle-fold the recording media at high torque. On the other hand, when a small number of recording media are saddle-folded, it is unnecessary to saddle-fold the recording media at high torque. With the technique explained above, since recording media are saddle-folded at low speed irrespectively of the number of recording media to be saddle-folded, a reduction in processing time for saddle folding is insufficient.